Processes for preparing sulfonylureas

ABSTRACT

Compounds of the formula I or salts thereof,   &lt;IMAGE&gt;   in which X is oxygen, -O-NR2- or -SO2-NR2-, and Y is N or CH, R1 is (C1-C6)alkyl, (C2-C6)alkenyl or (C2-C6)alkynyl, which are in each case optionally substituted, or, in the case where X=oxygen, also (subst.) phenyl, R2 is H, (C1-C6)alkyl, (C2-C6)alkenyl or -alkynyl or (C3-C6) cycloalkyl, R3 and R4 are H, (subst.) (C1-C4)alkyl or (subst.) (C1-C4)alkoxy or halogen, (C1-C4)alkylthio, (C1-C4)alkylamino or di[(C1-C4)alkyl]-amino, R5 is H or (C1-C4)alkyl and R6 is hydrogen, may be prepared by reacting compounds of the formula II, R1-X-R7(II) with compounds of the formulae III, IV and V R8-OCN(III) SO2Cl2(IV)    &lt;IMAGE&gt;  (V)   where R7 and R8 are H, a quarternary ammonium ion or one equivalent of a metal cation. The structure of the intermediate compounds has not been determined.

The invention relates to processes for preparing heterocyclicallysubstituted sulfonylurea herbicides, especially compounds of the formulaI, ##STR3## in which X is oxygen, --O--NR² -- or --SO₂ --NR² --,

Y is nitrogen or CH,

R¹ is (C₁ -C₆)alkyl, (C₂ -C₆)alkenyl or (C₂ -C₆)alkynyl, where each ofthe latter three radicals, independently of each other, is unsubstitutedor substituted by one or more radicals selected from the groupcomprising halogen, (C₁ -C₄)alkoxy and [(C₁ -C₄)alkoxy]-carbonyl, or, inthe case where X=oxygen, also phenyl, which is unsubstituted orsubstituted by one or more radicals selected from the group comprisinghalogen, nitro, (C₁ -C₄)alkyl, (C₁ -C₄)haloalkyl, (C₁ -C₄)alkoxy, (C₁-C₄)haloalkoxy and [(C₁ -C₄)alkoxy]-carbonyl,

R² is hydrogen, (C₁ -C₆)alkyl, (C₂ -C₆)alkenyl, (C₂ -C₆)alkynyl or (C₃-C₆)cycloalkyl,

R³ and R⁴ independently of each other, are hydrogen, (C₁ -C₄)alkyl or(C₁ -C₄)alkoxy, where each of the latter two radicals is unsubstitutedor substituted by one or more radicals selected from the groupcomprising halogen, alkoxy and alkylthio, or is halogen, (C₁-C₄)alkylthio, (C₁ -C₄)alkylamino or di[(C₁ -C₄)alkyl]-amino and

R⁵ is hydrogen or (C₁ -C₄)alkyl and

R⁶ is hydrogen,

and salts thereof with acids or bases.

Formula I also comprises all the unspecified possible stereoisomerswhich are definable by their specific shape in space, such asenantiomers, diastereomers and Z and E isomers, which possess thecombination of atoms given in formula I. Such compounds of the formula Icontain, for example, one or more asymmetric carbon atoms or doublebonds which are not especially indicated in the formula I. Thestereoisomers may be obtained by customary methods from mixtures of thestereoisomers or be prepared by stereoselective reactions in combinationwith the use of stereochemically pure starting materials.

The compounds of the formula I can form salts in which the hydrogen ofthe --SO₂ --NH-- group is replaced by a cation which is suitable, inparticular, for agriculture. These salts are, for example, metal salts,in particular alkali metal salts (e.g. with Na⁺ or K⁺ as the cation) oralkaline earth metal salts, or ammonium salts or salts with organicamines. Salt formation can also take place by the addition of a strongacid to the pyrimidine moiety of the compound of the formula I. Suitableacids for this purpose are strong inorganic and organic acids, forexample HCl, HBr, H₂ SO₄ or HNO₃.

Compounds of the formula I are known and are employed as plantprotective agents with herbicidal activity; see EP-A-013258(US-A-4,601,747), EP-A-0342569 (US-A-5,104,443) and EP-A-4163(US-A-4,191,553). In these said documents some processes according towhich compounds of the formula I can be prepared are also cited ordescribed.

A disadvantage of the known processes is the use of chlorosulfonylisocyanate (CSI), whose high reactivity gives rise to safety problemsand whose difficult obtainability leads to high costs. The knownprocesses are therefore unfavorable for implementation on the industrialscale, from the point of view of both safety and expense.

A novel process has now been found according to which compounds of theformula I can be prepared in a surprisingly efficient manner by thereaction of readily available starting materials.

The present invention relates to a process for preparing the saidcompounds of the formula I, or their salts, wherein compounds of theformula II,

    R.sup.1 --X--R.sup.7                                       (II)

in which R¹ and X are defined as in formula I and R⁷ is hydrogen, aquaternary ammonium ion or one equivalent of a singly, doubly ormultiply charged metal cation, are reacted with compounds of theformulae III, IV and V,

    R.sup.8 --OCN                                              (III)

    SO.sub.2 Cl.sub.2                                          (IV) ##STR4## in which R.sup.3, R.sup.4, R.sup.5, X and Y are defined as in formula I and R.sup.8 is hydrogen, a quaternary ammonium ion or one equivalent of a singly, doubly or multiply charged metal cation.

Those processes according to the invention for preparing compounds ofthe formula I are of particular interest in which R¹ --X is N[(C₁-C₆)-alkylsulfonyl]-N-[(C₁ -C₃)alkyl]-amino or [(C₁ -C₄)alkoxy]-phenoxy,R³ and R⁴, independently of each other, are (C₁ -C₂)alkyl or (C₁-C₂)alkoxy and R⁵ is hhydrogen or methyl and R⁶ is hydrogen.

R¹ --X is preferably N-[(C₁ -C₃)-alkylsulfonyl]-N-[(C₁ -C₂)alkyl]-amino,in particular N-(methylsulfonyl)-N-(methyl)-amino,N-(methylsulfonyl)-N-(ethyl)-amino, N-(ethylsulfonyl)-N-(methyl)-aminoor N-(n-propylsulfonyl)-N-(methyl)-amino; R¹ --X is also preferably (C₁-C₃)-alkoxyphenoxy, in particular 2-methoxyphenoxy, 2-ethoxyphenoxy,2-n-propoxy-phenoxy or 2-isopropoxyphenoxy.

R³ and R⁴ independently of each other, are preferably (C₁ -C₂)alkyl or(C₁ -C₂)alkoxy, in particular methyl or methoxy.

Examples of R⁷ and R⁸ are alkali metal cations or alkaline earth metalcations such as sodium ions, potassium ions, magnesium ions and calciumions. In the case of metal cations with a charge of more than 1, two ormore radicals of the formula R¹ --X in compounds of the formula II andseveral of the radicals OCN in compounds of the formula III arecorrespondingly bound to the metal ions. Examples of R⁷ and R⁶ are alsoquaternary ammonium ions such as tetraalkylammonium,trialkylarylammonium, dialkyldiarylammonium, alkyltriarylammonium andtetraarylammonium, where the alkyl radicals may, where appropriate, besubstituted, e.g. by alkoxy or aryl.

In the said formulae and below, hydrocarbon-containing radicals such asfor example, alkyl, alkoxy, haloalkoxy and alkylthio radicals, as wellas the corresponding unsaturated and/or substituted radicals in thehydrocarbon moiety, can in each case be straight-chain or branched.Alkyl radicals, in the composite senses such as alkoxy, haloalkyl etc.,as well, are methyl, ethyl, n- or i-propyl, n-, i-, t- or 2-butyl;alkenyl and alkynyl radicals have the meaning of the possibleunsaturated radicals corresponding to the alkyl radicals, such as2-propenyl, 2- or 3-butenyl, 2-propynyl or 2- or 3-butynyl. Halogen isfluorine, chlorine, bromine or iodine. Haloalkyl is alkyl which issubstituted by one or more atoms selected from the group comprisinghalogen; haloalkyl is, for example, CF₃, CHF₂ or CH₂ CF₃. Aryl is, forexample, phenyl, naphthyl, tetrahydronaphthyl, indanyl, fluorenyl andthe like, preferably phenyl. Substituted aryl or substituted phenyl ispreferably aryl or phenyl which is substituted by one or more,preferably 1 to 3, radicals selected from the group comprising halogen,alkyl, haloalkyl, haloalkoxy, nitro, cyano, alkoxycarbonyl, alkanoyl,carbamoyl, mono- and di-alkylaminocarbonyl, mono- and di-alkylamino,alkylsulfinyl or alkylsulfonyl, where the preferred alkyl-containingradicals are those with 1 to 4 carbon atoms, in particular 1 to 2 carbonatoms; particularly preferred in this context are methyl, methoxy andchlorine.

The yields of the resulting sulfonylureas of the formula I, as preparedby the process according to the invention, are relatively high, e.g. 80%and more, with purities of more than 94% by weight being obtained,generally without elaborate purification steps.

The reaction is preferably carried out in two or more stages. In thefirst of these the compounds of the formulae II, III and IV are reactedwith each other. Then compounds of the formula V are added to thereaction mixture obtained in this way. Intermediates arising inconjunction with the mixing of the reactants can be isolated as a rule.However, the whole process may also be carried out as a one-pot process.

The temperatures for the reactions of the components II, III and IV arepreferably between 0° C. and +200° C., in particular between +80° C. and+135° C., very particularly between +20° C. and +90° C.

The temperature for the reaction of the reaction mixture consisting ofII, III and IV with the aminoheterocycle V is preferably between -20° C.and +120° C., in particular between -5° C. and +80° C.

The process according to the invention may be carried out withoutsolvents. However, it is often advantageous to carry out the process, orindividual stages of the process, in the presence of inorganic ororganic solvents which are inert under the reaction conditions, or inmixtures of these solvents. It can also be advantageous to change thesolvent between the component stages of the process.

Suitable organic solvents are, for example, aprotic polar organicsolvents, such as aliphatic or aromatic nitriles,N,N-dialkyl-alkanecarboxamides, dialkyl sulfoxides, polyalkylene glycoldialkyl ethers and N-alkylated cyclic amides, and aliphatic or,preferably, aromatic, where appropriate halogenated, hydrocarbons, ormixtures of the said organic solvents. Suitable inorganic solvents are,for example, liquid sulfur dioxide and liquid hydrocyanic acid, andtheir mixtures. Mixtures of the said organic and inorganic solvents arealso possible.

Solvents which are preferred are those such as, for example,acetonitrile, propionitrile, benzonitrile, dimethylformamide, dimethylsulfoxide, sulfolane, N-methylpyrrolidone, ethylene glycol dialkylethers, di-, tri- or tetra-ethylene glycol dialkyl ethers, in particulardimethyl or diethyl ether, toluene, xylene, chlorobenzene or liquidsulfur dioxide, or mixtures of two or more of the said solvents. It canalso be particularly advantageous to carry out the first component stageof the process, i.e. reactions of II, III and IV, or of II and IV, in apolar aprotic organic or inorganic solvent, for example, such asacetonitrile or liquid sulfur dioxide, and to carry out the followingstage(s) in less polar aprotic organic solvents, for example, such astoluene or xylene.

In those cases where compounds of the formula II and/or the formula IIIare not completely soluble in the chosen solvent, the reaction can bespeeded up by very thorough mixing of the reactants, for example bymeans of vigorous stirring or by sonication.

In reacting the compounds of the formulae II, III and IV, the compoundsof the formulae III and IV can, for example, be reacted first, forexample at a reaction temperature of 0° to 80° C. without solvent or inthe presence of one of the said aprotic polar organic or aprotic polarinorganic solvents, resulting in the formation of an addition compoundof indeterminate structure (adduct 1). After that the reaction of IIwith the previously obtained adduct 1, most simply in the form of thepreviously obtained reaction mixture, is carried out, where appropriatewith heating, resulting once again in the formation of an additioncompound of indeterminate structure (adduct 2), which is suitable forthe reaction according to the invention with the compound of the formulaV. The reaction with the compound II is effected, for example, at areaction temperature of 0° to 200° C., preferably of +8° C. to +135° C.,in particular of +20° C. to +90° C. in the presence of one of the saidaprotic polar organic or aprotic polar inorganic solvents. It isfrequently advantageous to carry out the said reactions of the compoundsII, III and IV using an ascending temperature gradient rather than atconstant temperature.

According to results of investigations with detection reactions andspectroscopic methods, the addition compounds arising as intermediatesdo not, as initially thought, comprise an isocyanate of the formula R¹XSO₂ --N═C═O, although, when viewed formally, the reaction of adduct 2with the amine of the formula V to yield the substituted urea of theformula I at least gives the same result as would be expected from thereaction of an isocyanate of the formula R¹ XSO₂ NCO with the amine ofthe formula V.

The invention therefore also relates to the said adducts 1 and 2 whichcan be obtained by the said variants of the reactions of compounds IIIand IV and of the subsequent reaction with compound II according to theprocess according to the invention.

In an alternative embodiment, the compounds of the formulae II, III andIV can be introduced together, preferably at a low temperature down to-10° C. or less, and heated together to the reaction temperature. In afurther variant of the process the compounds of the formulae II and IIIcan be introduced together and the sulfuryl chloride (compound of theformula IV) can be added either before heating to the reactiontemperature or at the reaction temperature of the reaction of thecompound of the formula II.

The reaction of the compounds of the formulae II, III and IV ispreferably carried out under aprotic conditions.

In those cases where R⁷ or R⁸, or both, are hydrogen, it is, as a rule,expedient to employ one mole equivalent of an auxiliary base for eachmole equivalent of hydrogen. Inorganic bases such as, for example,alkaline earth metal carbonates and/or bicarbonates, alkali metalcarbonates and/or bicarbonates, and similar bases, or organic bases,such as, for example, trialkylamines, may be used as auxiliary bases.

In the case where R⁷ is=hydrogen, it is as, as a rule, advantageous toemploy the compounds of the formulae II and III, in which R⁸ is notidentical to hydrogen, in the molar ratio II:III of at most about 1:2,in particular in the molar ratio of about 1:2, with at least one moleequivalent of the compound III serving as the auxiliary base. If a molarratio II:III of about 1:1 is also used in the case where R⁷ is=hydrogen,it is advantageous for complete reaction to employ at least about oneequivalent of another auxiliary base or, if, in addition, R⁸is=hydrogen, at least two equivalents of another auxiliary base. Thebases mentioned in the previous paragraph can be employed as theauxiliary bases.

In the case where R⁷ and R⁸ are each a metal cation or quaternaryammonium cation, the compounds II and III can also be employed withoutan auxiliary base, in the molar ratio of about 1:1.

Sulfuryl chloride (compound of the formula IV)is preferably equimolar tothe compound of the formula II, or is employed in excess, for example inthe molar ratio II:IV of 1:1 to 1:2, preferably 1:1 to 1:1.5. Largerexcesses are also possible. It is, as a rule, expedient to remove bydistillation sulfuryl chloride which has been added in excess beforeadding the compounds of the formula V.

The compounds of the formula V may be employed in an equimolar ratio tocompounds of the formula II, or in less than equimolar or greater thanequimolar ratio. Unreacted portions of V can be separated out of thereaction mixture by customary methods and reemployed for the process.

The starting compounds of the formulae III and IV required for preparingthe compounds of the general formula I by the process according to theinvention are available commercially or can be readily prepared by wellknown methods. The compounds of the formula II are either availablecommercially or can be prepared by analogy with customary methods, e.g.by means of reacting sulfochlorides with amines.

The heterocycles of the formula V are also either available commerciallyor can be readily prepared by suitable methods; see, e.g.,US-A-4,310,470, EP-A-0027200, US-A-4,299,960, M. J. Langermann, C. K.Banks, J. Am. Chem. Soc. 73, 3011 (1951).

An advantage of the process according to the invention is that thoseportions of the compounds of the formulae IV and V which have notreacted, as well as the solvents which have been used, can be recoveredvirtually quantitatively and be reemployed in the process.

Secondary components which are not readily soluble, such as, forexample, sodium chloride, may also be separated off between the reactionstages.

An additional advantage of the process according to the invention isthat, as a rule, the desired products of the formula I, as compoundswhich are not readily soluble, precipitate out, where appropriate afterthe addition of water or other polar solvents, in high purity from thereaction medium.

In the following examples the percentage values relate to weight, unlessotherwise indicated.

EXAMPLES 1.1-[(N-Methylsulfonyl-N-methyl-amino)-sulfonyl]-3-(4,6-dimethoxy-2-pyrimidyl)-urea

340 g (2.52 mol) of sulfuryl chloride are introduced into 1.5 l ofacetonitrile, and 260 g (4.0 mol) of sodium cyanate are added inportions within the space of 20 min while stirring vigorously (20° C.).The mixture is stirred for a further 15 min and then 222 g (2.0 mol) ofN-methylmethanesulfonamide are added dropwise at 25° C., the temperatureis raised slowly and the mixture is heated to reflux for 200 min whilestirring vigorously. Subsequently, the excess sulfuryl chloride isdistilled off with the solvent under 100 mbar up to an internaltemperature of 50° C. After releasing the pressure under nitrogen, 1.5 lof acetonitrile (optionally also toluene etc.) are added and 155 g (1.0mol) of 2-amino-4,6-dimethoxy-pyrimidine are introduced at 0° C. After75 min, 1.0 l of water is added and the precipitate is separated off andwashed. 304 g of1-[(N-methylsulfonyl-N-methyl-amino)-sulfonyl]-3-(4,6-dimethoxy-2-pyrimidyl)-ureaare obtained with a melting point of 176° to 178° C. The product is inaccordance with a comparison sample and, according to analysis by highpressure liquid chromatography (HPLC), has a purity of 96%; yield: 77%of theory.

2. 1-(2-Ethoxyphenoxysulfonyl)-3-(4,6-dimethoxy-2-pyrimidyl)-urea

26.0 g (0.4 mol) of comminuted sodium cyanate are suspended at roomtemperature in 200 ml of acetonitrile, and 28.3 g (0.21 mol) of sulfurylchloride are added within the space of 20 min, during which time thetemperature rises to 44° C. After stirring for a further four hours at50° C., the mixture is distilled under reduced pressure, cooled to 27°C. and 27.6 g (0.2 mol) of 2-ethoxyphenol are added within the space of10 min. The mixture is left to stand overnight and 15.5 g (0.1 mol) of2-amino-4,6-dimethoxypyrimidine are added at room temperature. Themixture is stirred at 50° C. for a further 120 min, the solvent isremoved under reduced pressure, 100 ml of water are added, and themixture is extracted with dichloromethane. After distilling off theorganic solvent, 49.9 g of solids remain which, according to HPLC,exhibit a content of 71.6% by weight of1-(2-ethoxyphenoxysulfonyl)-3-(4,6-dimethoxy-2-pyrimidyl)-urea. Theyield of the compound is about 89% of theory.

The compounds of the formula I (Y═CH) listed in the following table arealso obtained in analogy with the Examples 1 and 2.

    __________________________________________________________________________    Example                                                                            R.sup.1 X        R.sup.3                                                                           R.sup.4                                                                          R.sup.5                                                                         R.sup.6                                                                          m.p.[°C.]                            __________________________________________________________________________     3   CH.sub.3                                                                              SO.sub.2 N(C.sub.3 H.sub.7)                                                            CH.sub.3                                                                          CH.sub.3                                                                         H H  154-157                                      4   CH.sub.3                                                                              SO.sub.2 N[CH(CH.sub.3).sub.2 ]                                                        CH.sub.3                                                                          CH.sub.3                                                                         H H  120-122                                      5   C.sub.2 H.sub.5                                                                       SO.sub.2 N(C.sub.2 H.sub.5)                                                            CH.sub.3                                                                          CH.sub.3                                                                         H H                                               6   CH.sub.3                                                                              SO.sub.2 N(CH.sub.3)                                                                   CH.sub.3                                                                          CH.sub.3                                                                         H H                                               7   CH.sub.3                                                                              SO.sub.2 N(CH.sub.3)                                                                   CH.sub.3                                                                          CH.sub.3                                                                         H CH.sub.3                                        8   C.sub.4 H.sub.9                                                                       SO.sub.2 N(CH.sub.3)                                                                   CH.sub.3                                                                          CH.sub.3                                                                         H H                                               9   CH.sub.3                                                                              SO.sub.2 N(cyclohexyl)                                                                 CH.sub.3                                                                          CH.sub.3                                                                         H CH.sub.3                                       10   2-i-PrO--C.sub.6 H.sub.4                                                              O        OCH.sub.3                                                                         CH.sub.3                                                                         H H  141-143                                     __________________________________________________________________________     i-PrO = isopropoxy                                                       

I claim:
 1. A process for preparing compounds of the formula I or saltsthereof, ##STR5## in which X is oxygen, --O--NR² -- or --SO₂ --NR.sup.2--,Y is nitrogen or CH, R¹ is (C₁ -C₆)alkyl, (C₂ -C₆)alkenyl or (C₂-C₆)alkynyl, where each of the latter three radicals, independently ofeach other, is unsubstituted or substituted by one or more radicalsselected from the group consisting of halogen, (C₁ -C₄)alkoxy and [(C₁-C₄)alkoxy]-carbonyl, or, in the case where X=oxygen, also phenyl, whichis unsubstituted or substituted by one or more radicals selected fromthe group consisting of halogen, nitro, (C₁ -C₄)alkyl, (C₁ -C₄)haloalkyl, (C₁ -C₄)alkoxy, (C₁ -C₄) haloalkoxy and [(C₁-C₄)-alkoxy]-carbonyl, R² is hydrogen, (C₁ -C₄)alkyl, (C₂ -C₆)alkenyl,(C₂ -C₆)alkynyl or (C3-C₆) cycloalkyl, R³ and R⁴,independently of eachother, are hydrogen, (C₁ -C₄)alkyl or (C₁ -C₄)alkoxy, where each of thelatter two radicals is unsubstituted or substituted by one or moreradicals selected from the group consisting of halogen, alkoxy andalkylthio, or is halogen, (C₁ -C₄)alkylthio, (C₁ -C₄)alkylamino ordi[(C₁ -C₄)alkyl]-amino and R⁵ is hydrogen or (C₁ -C₄)alkyl and R⁶ ishydrogenwherein compounds of the formula II,

    R.sup.1 --X--R.sup.7                                       (II)

in which R¹ and X are defined as in formula I and R⁷ is hydrogen, aquaternary ammonium ion or one equivalent of a singly, double ormultiply charged metal cation, are reacted in a one-pot process or intwo or more stages with compounds of the formulae III, IV and V,

    R.sup.8 --OCN                                              (III)

    SO.sub.2 Cl.sub.2                                          (IV) ##STR6## in which R.sup.3, R.sup.4, R.sup.5, X and Y are defined as in formula I and R.sup.8 is hydrogen, a quaternary ammonium ion or one equivalent of a singly, doubly or multiply charged metal cation, and wherein during the process, the compounds of formulae III and IV are reacted resulting in formation of an addition product (adduct 1).


2. The process as claimed in claim 1, whereinR¹ --X is N[(C₁-C₆)-alkylsulfonyl]-N-[(C₁ -C₃)alkyl]-amino or [(C₁ -C₄)alkoxy]-phenoxy,R³ and R⁴, independently of each other, are (C₁ -C₂)alkyl or (C₁-C₂)alkoxy, R⁵ is hydrogen or methyl and R⁶ is hydrogen.
 3. The processas claimed in claim 1, wherein R¹ --X is N-[(C₁-C₃)-alkylsulfonyl]-N-[(C₁ -C₂)-alkyl]-amino or (C₁ -C₃)-alkoxyphenoxy.4. The process as claimed in claim 1, wherein R³ and R⁴ are methyl ormethoxy.
 5. The process as claimed in claim 1, wherein the compounds ofthe formulae II, III and IV are first reacted with each other and thereaction with compounds of the formula V is carried out thereafter. 6.The process as claimed in claim 5, wherein the reaction temperature forthe reactions of the compounds of the formulae II, III and IV is between0° C. and 200° C.
 7. The process as claimed in claim 5, wherein thereaction temperature for the reaction with the compound of the formula Vis between -20° C. and 120° C.
 8. The process as claimed in claim 1,wherein the process or individual stages of the process are carried outin the presence of inorganic or organic solvents which are inert underthe reaction conditions, or in mixtures of these solvents.
 9. Theprocess as claimed in claim 8, wherein a solvent is employed selectedfrom the group consisting of aprotic polar organic solvents andaliphatic and aromatic, where appropriate halogenated, hydrocarbons, andmixtures of the said organic solvents.
 10. The process as claimed inclaim 1, wherein the compounds of the formulae II, III and IV arereacted under aprotic conditions.
 11. The process as claimed in claim10, whereinR⁸ is a metal cation or a quaternary ammonium cationand thecompounds of the formulae II and III are employed a) in the case whereR⁷ =H, in a molar ratio of at most 1:2 or b) in the case where R⁷ =H, ina molar ratio of about 1:1 and in the presence of 1 mole equivalent ofan auxiliary base which is different from compound III or c) in the casewhere R⁷ =metal cation or quaternary ammonium cation, in a molar ratioof about 1:1 without auxiliary base.
 12. The process as claimed in claim1, wherein the compound of the formula IV is equimolar to the compoundof the formula II, or is employed in excess.